Method of manufacture of cathode ray tubes



July 12, 1960 H. R. coLGATE v METHOD oF MANUFACTURE og cATHoDE RAY TUBES Filed Jan. 12, 1959 /7 //7 Vf/ j: /v ////////`//V7 f K /0 /3 /4 /f /6' United! States Patent e 'METHOD- 0F A'CTURE 0F 'CATHDE t RAY TUBES 1Harry "R. Colgate, 'Redondo 'Bea-ch, Calif., assignor to Philco Corporation, Philadelphia, Ta., a corporation s plicable vtothe manufacture of cathoder ray tubes having index "elements "which, in response to ele'ctro'n beam impingernent, produce an index signal f(e.'g. bylifght emis-l sion ,or Vsecondary 'electron emission)l indicative `4of t-he rate of beam traversal of the screen and of the position ofthe beam at anyinsta-nt. f l

While not limited -thereto, the invention risfparticu- -larly applicable land will'be described with reference to the manufacture of color image-producing ycathode ray tubes for use in color television `receivers wherein `an index vsignal is utilized to coordinate the instantaneous` beam modulation, 'and the instantaneous beam position to insure proper color rendition, l'and it is very important that the yindex elements rbe accurately located. In a preferred form of sucha cathode ray tube, the screenhas phosphor stripes Aextending transversely tothe direction of line scanning `and arranged in successivetriplets, the lstripes of each triplet being Ysuccessively emissivefot` light of different primary colors (ergL red,' green and blue) in response to electron beam impingement during each line "scan of the screen, and the screen also has index ystripes `associated with the color,` triplets. .In order lto increase the light VOutput from the `vcreenand f thus "increase the brightness of 'the reproduced image, an lelectron-perme- ICC areaon'to at least ,a -portion of 'the 'wall of the 4bell por- 'jtion of 'the tube envelope, particularly Where the ,index signal is to be lproduced by light emission o'f the 'index elements. The present practice is to have the light-reecting lm extend over substantially the entire wall of the bell portion a's this enhances the production o'f the index signal. Moreover, it is also desirableito provide index elements not'r only on .the 'screen varea but Yalsoizm thewall area adjacent thereto so'that'the index signal will be generated throughout the ventire 'trace 'of the electron beam. The presentpractice, 'as described on 'pages 11115 to l1119 of the Proceedings ofthe LRIE. forSepten-ib'er 1956, is to form the renvelope `unit comprising the face plate and the bel'ljportion, and then carry outt'he 'aforementioned process using back projection of light. 'However, the provision of Aindex elements on 'the 'wall larea gave rise to a problem 'in that light directed to thewa'll varea for location of index elements 'thereon tends to be Vreflected 'by the aluminum film to portions of lthe screen In accordance with this invention, the aforementioned undesired-reflection of light in the practice of 'the photographic vmethod is `prevented by applying `to the lightrelecting 'lm .a material which is non-reflective ofthe flight 'to which `the photosensitive layernext to ibe applied is sensitive. Thus the `rnetl'io'd according to 'this linvention includes not only the steps. previously followed `but also 'an intermediatelst'ep following `the application of the light-reflecting lm and prior to the application of Ithe f photosens'itive :layer forthe deposition of Vthe elements,

u -e.g. index elements, which 'are applied :to fthe screen "and able light-reflecting iilm, preferabiy composed of alumi- Experience has shown Ythatvt'lne 'best method of apply- Y num, is provided behind the :colored llight-emissive'e'lef Cathode ray tubes of the y'stated character are ,now well wallfareas. f ,'f

The invention-'may be :ful-ly understood Afrom th'e zfollowing detailedfdescription with reference ,tol the -accompanying vdrawing wherein the single ligure is a sectional view taken :horizontally through :the-axis of a ycolor vimage-producing cathode ray tube manufactured in accordance with the present invention.- Itt Willbe understood that it is impossible to illustratez-on .true scale the multitudinous extremely fine elements as theyexis't in the physical structure, and rtherefore ytheillustration is ing the colored 'light-emissive elements and the index yelef ments is the photographic method which involves, for each set of elements, application' of 'a photosensitve layer f (i.e. a vphotograjgihi'c emulsion), selectivejlight exposure through a suitable Amask jofthose areas of said layer where the elements areto be provided, and removalof'the exposed portions of said layer.v 'They light exposed portions are rendered insoluble, and it is a simple matter to remove theY unexposed portions simply bywashing bellY portion 11.

Serial No. 248,356, filed September'26, 19151, anda 'c of pending application of M. Sadowsky andi-S. lL. iPa-rsons, Serial No. 408,219Jgled Fehrua1y4, 1954.

In cathode ray tubes employing a light-reflecting film, such asV the aforementioned aluminum film, it is generally desirable to have this film' extend beyond the screen tion. 'each instance may be regarded as emanating `from :a

intended-only to be Ygenerally.vreiirresentativelof vthe structure. Y

Referring moreparticularly to the drawing, the envelope unit shown comprises the kface plate 10 andthe In .thephotogra-phic process as presently practiced, a light pattern -of each set -of elements to be deposited is projected from the rear throughthe bell por- For simplicity of illustration, the light pattern ,in

point 12, although it will beunderstoo'd that in actual practice light projection -apparatus'including a mask iis used to produce each light pattern, as described in .the aforementioned Proceedings -of the LRE. As hereinbefore stated, the colored light-emissive elements 13 are lirst appliedto the .face plate 10,l and the light-reflecting film 14, preferably composed A of aluminum, is then `applied. In the illustration Vthis vfilm is shown extending over the-wall area adj acentto the screen area, and in some instances it maybe desired to have the film extend .over substantially the entire, wall yarea of :the bell portion 1,1, which in fact is the present practice.

In accordance with the present invention, the next step in the overall procms is the application to the light-ret Patented July 12, 1960'v j 3 ecting iilm 14 of a coating 15 of material which is nonrellective of light of a particular vcolor to which the photosensitive layer next to be applied is sensitive. This Coating can be applied. as a liquid in anysuitable manner as by painting, and it need only be a thin coating which covers the lm 14. Preferably, the material 15 is a red dyeY which is non-reflective of blue light to which v.the usual photographic emulsion is sensitive. If desired, the dye can be added to the lacquer which is commonly yapplied to the aluminum lm as a protective film. The

coating 15 extends over the screen area and the adja cent wall area. Anysuitable material may be used for the coating 15 which can be later baked out without leaving a residue. For example, the oil dyes which are used to color gasoline and leave no residue when baked out can be used for the coating 15. i

. Following the application of the coating 15, the photosensitive layer 16 isV applied and those areas'thereot where the index elements are to be vprovided are selec- -tively exposed tov light, after which the unexposed portions of layer 16 are removed as by washing them away lwith water in which the unexposed emulsion leaving the index elements 17. Y

Prior to this invention, in the absence of the coating 15,` a problem was presented with respect to the provision of index elements on thewall area adjacent to the screen jarea. Consider, for example, the light` ray 18 impinging on the photosensitive layer 16 to provide index element' 17a. In the absence of the coating 15, all of the light of'this ray would be reflected by the reflecting film 14, Vas indicated by the dotted line 19, and the result would be that portions of the layer 16 where no index elements are desired would be rendered insoluble, thus degrading the index pattern. However, with the coating 15 pres- "ent, the light to which the layer 16 is sensitive is not reflected by the iilm 14. Thus this invention provides a very simple solution to the problem.v

The nal vstep. in the process is the removal of the coating 15by baking. The usual baking operation, to which `cathode ray tubes are commonly subjected, will serve to remove the coating 15 without leaving a residue.

From the foregoing description it will be seen that the present invention has provided Vavery simple solution to a real problem; Moreover, the invention is applicable in. anyinstance where it is desired to apply elements to I.theV screen and adjacent wall area lof acathode ray tube. It will beunderstood, therefore, that no limitation of `the invention is intended herein except as defined by the .appended claims. 1

I claim: i

is soluble,

V applying a light-reflecting film tothe screen area arid l. In the'manufacture of cathode ray tubeswherein it is` desired to provide for light reflection and also to. provide elements on the screen and on the wall area ad` Y --jacent thereto, the method which includes the steps of applying a light-reflecting film to the screen area and also .at least to the adjacent wall area, applying to the lightreflecting film a material which is non-rellective of light of a particular color, applying over said material a photosensitive layer which is sensitive to light of said particuvlar color, selectively exposing to light those areas of said layer where said elements are to be provided, and renoving said material and the unexposed areas of said ayer.

2. In the manufacture of cathode ray tubes wherein `itis desired to provide for light reflection and also to :provide elements on the screen and on the wall area ad- -jacent thereto, the method which includes the steps of 'gapplying a light-reflecting film to the screen area and also fat "least to the adjacent 'wall area, applying to the light- 'reflecting lm a material which is non-reflective of light .of a particular color and which can be removed later by also at least to the adjacent wall area, applying to the light-reflecting flm aV red dye whichlis non-reflective of blue light and which can be removed later by barking, applying over said'dye a soluble photosensitive 'layer which is rendered insoluble by blue light, selectively exposing to light those areas of said layer where said elements are to be provided, dissolving the unexposed areas lof said layer, and removing said dye by baking.

4. In the manufacture of color image-producing cathode -ray tubesof the index type whereinit is desired to provide for light reflection and `also to provide vindex elements on the screen and on the wall area adjacent thereto, the method which includes the steps of applying to the screen elements emissive of light of differentcolors when impinged by anv electron beam, applying a lightreilecting lm'to the screen area containing said elements and also at least to the adjacent wall area, applying to the light-reecting iilm a material which is non-reflective of light of a particular color, applying oversaid Ina'- terial a photosensitive layer which is sensitive to light of said particular color, selectively exposing to light those areas of said layer where the indexl elements are to be provided, and removing said material and the unexposed areas of said layer. k

5. In the manufacture of color image-producing cathode ray tubes of the index type wherein it is desired to provide for light reection and also to provideindex elements on the screen and o n the wall area adjacent thereto, the method which includes the steps of applying to the screen elements emissive of light of diercnt colors when impinged by an,V electron beam, applying a lightreecting'lm to the screen area containing said Velcrnents and also at least to the adjacent wall area, applying to the light-reflecting lm a material which is nonreective of light of a particular color and whichy can be removed later by baking, applying over said material a soluble photosensitive layer which is rendered insoluble by light of said particular color, selectively exposing toV light those areas of said layer where the index elements are to be provided, dissolving the unexposed areas of said layer, and removing said'm'aterial by bak- 6. In the manufacture of color ima'gefproducing cathode ray tubes of the index type wherein it is desired to provide for light reflection and also to provide index elements on the screen vand on the wall area vadjacent 'non-reflective of blue light and which can Vbe removed `later by baking, applying over said dye a soluble photosensitive layer which is rendered insoluble by blue light, selectively exposing to light those areas of said layer where the index elements are to be provided, dissolving the unexposed areas of said layer, and removing said dye by baking.

No references cited. 

